A CAN-bus (Controller Area Network-bus) system or, generally speaking, a system in which a shared media is accessed and used to transmit data, requires that all nodes accessing the medium or the bus adhere to a common timing schedule. Thereby, a CAN-bus node may be an electronic control unit (ECU) that controls one or more of the electrical systems or subsystems e.g. in a motor vehicle. To this end, some systems that do not distribute a common clock signal, such as a CAN-bus, require that each node of the system provides its own clock signal which typically means that each node contains an oscillator. The oscillator of each node defines at which time instance a signal is sampled or transmitted to the bus. In nodes for CAN-buses, for example, the oscillator often has a cycle time which is shorter than the bit-time used to transmit or signal the value of a single bit on the bus. According to a CAN-bus specification, a single bit-time may correspond to a predetermined nominal number of cycles or oscillations of the internal oscillator.
In order to avoid bit-errors on the bus caused by wrong sampling times or wrong transmission times of individual nodes, the local oscillators of all nodes shall be synchronized with each other. While the CAN-bus foresees hard-and-soft synchronization mechanisms, the requirement for the nodes' oscillators are still high in order to not lose synchronization in between the hard- or soft-synchronization events. Accurate oscillators, however, are expensive and may sometimes only be implemented as an additional external oscillator, which is an additional component within a CAN-bus node or a CAN-bus communication controller. This in turn leads to increased assembly costs and increased size of the circuitry of the device.